By Adrian Cho in Washington DC PICTURES from a commercial satellite are sharp enough to reveal activity at nuclear plants throughout the world, says a nuclear arms expert. These pictures cost just a few thousand dollars each, so even poor nations can keep tabs on whether their neighbours are developing nuclear weapons. While the best American satellites can spot shoebox-sized objects, only a handful of other countries have satellites sophisticated enough to tell whether plutonium-producing reactors and other weapons facilities are active. But that’s changing, thanks to the IKONOS satellite,